Research School of Earth Sciences
Earth Physics - Seismology
Tracing the Craton Edge - Tasman Line and Central Australia
20 sites were installed in May 2003 spanning the Tasman Line and crossing from the southern to the northern Australian Cratons. The first deployment of 6 southern stations took 8 days round trip from Canberra and, after a ten day break, the remaining 14 stations were deployed over an 18 day interval, with a total travel distance of some 12000 km. The stations extend from Hopetoun in Victoria to near Normanton in Queensland and nearly all are on rocky or stony ground which should provide good coupling for the seismometers. The majority of sites employ the new Earth Data recorders.
The design of the experimental configuration is based on simultaneous recording on both sides of the Tasman line which was not achieved in the earlier Skippy deployments. STS-2 seismometers have been installed at four locations with the object of achieving longer period recording for surface wave analysis. Most of the remaining sites use Guralp CMG3-ESP seismometers.
The instruments are grouped into a number of roughly linear profiles crossing the craton boundaries. A cluster of stations in NSW and South Australia should help to resolve the nature of the edge of the craton at depth around the Broken Hill region where there are some discrepancies between results from delay times from short-period stations and surface wave tomography. Nearly north-south profiles can be constructed on both sides of the Tasman Line linking to the permanent stations at WRA and CTAO. All the sites are new and are designed to link in with the placement of stations in the first four Skippy stages to achieve coverage at around the 200-300 km level.
The broad band stations will be operated for at least one year with servicing in October 2003 and April 2004. The data will be used in a number of ways exploiting both body waves and surface waves. We anticipate undertaking receiver function studies at each site to improve knowledge of crustal and uppermost mantle structure. Refracted wave information for both P and S phases at the northern sites will help to refine knowledge of transition zone structure. For the surface waves we will include data from the TL sites in the ongoing development of 3-D models of shear wavespeeds. We are also trying to extend methods using transfer functions between waveforms at different stations to achieve higher frequency analysis and thus improved resolution of structure.
Configuration of TL stations and the approximate location of the Tasman Line and Craton boundaries.
Questions about the topics in this Report to Brian Kennett: Brian.Kennett@.anu.edu.au
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